How much does a house extension cost? We get asked this question a lot, so, we thought it worthy of its own post!

It’s not an easy question to answer and obviously depends on a number of factors (etc, etc…), but that’s not the answer you’re looking for is it? You’re really looking for a very rough figure, a general guideline, a starting point.  OK, I’ll try my best.

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Let’s start with a basic single storey extension

say 4m x 5m


Figures have been updated in 2022 following recent price increases in constructions costs, according to a survey of architects and designers on Design for Me.

You may have heard that the rule of thumb is £1,000-£1,200 per m2. However, this figure is now somewhat out of date. From experience, £2000 per m2 is a now a more realistic estimate for a basic / mid-range house extension. In London and some parts of the South East, these figures could be between £2,300-2,800 per m2. See our separate post on house extension costs in London and the South East here.


So, for your 4 x 5m extension, the build cost would be roughly £40,000.

  • Add on 10-15% for professional fees (architect, planning application, building regs, structural engineer) (£6,000  at 15%)
  • VAT (£8,000)

Single storey house extension cost = £54,000+


How about a double storey extension, same footprint?

As a rule of thumb you can add 50% extra to the build cost of a single storey extension.

So, £40,000 +50% = £60,000 for the basic build cost

  • Add on 10-15% for professional fees (architect, planning application, building regs, structural engineer) (£9,000 at 15%)
  • VAT (£12,000)

Double storey house extension cost = £81,000+


The above figures would apply to a typical, uncomplicated extension in most parts of the UK. However, you should consider that these figures would creep up if any of the following apply:


Does it include a kitchen or bathroom?

  • Add £5,000 for a bathroom. Costs may be more depending on your sanitary ware and finishes.
  • Add £10,000 for a kitchen (again, completely depends on your specification, £10,000 should get you a lower-mid range kitchen with appliances)


Finishes and fittings

Above costs assume modest finishes, fittings, electrics and lighting. Think simple painted walls, carpet floors or possibly engineered oak.

  • If you’re wanting higher-end finishes e.g. tile finishes, fitted joinery etc the costs will increase.
  • Glazing will increase the cost also. Sliding or folding doors are a popular addition to extensions at the moment.


Are there any complex site constraints?

Your builder will need to include additional costs in their quotation if any of the following apply:

  • Your soil type and ground conditions may present more costly construction methods / techniques.
  • Limited access to the site. Will it be easy for the builder to bring in tools and machinery easily?
  • Existing structure. Are you removing any structural walls? If so there will likely be additional costs for steelwork.
  • Are you moving any pipework, drainage, gas meters?



  • As already mentioned above, in the South East you can expect to pay more than the rest of the UK, and notably more in London.


Materials and construction techniques

  • Consider the type/ quality of construction materials involved and the type of construction.


Managing or reducing your project costs

1. It pays to get professional advice from a good architect. They can help you realise the main ambitions for your extension, whilst helping control your costs. They will work with you to make sure you get the most out of your budget to recommend where your budget is best spent, and where costs would be unnecessary or could be minimised.

2. Make sure you get 3-5 quotes from recommended builders (your architect can help compile a tender list for you) to get a firm idea of the costs before starting work.

Your architect can also help you with your building contract, to prevent any nasty surprises down the line. They can also inspect the builder’s work to ensure it’s being carried out in accordance with the agreed design and specifications.

3. Shop around. Designers and contractors are often able to to access trade discounts.



Finding the right architect

Choosing the right architect for your home project is a critical first step, but can also be a bit of a minefield. This is exactly why I set up this website in the first place!

As well as being founder of, I am also a qualified architect. I found that many homeowners search online to find well established or high-end practices (it makes sense – these companies have bigger marketing budgets with stylish websites). However, such practices are often too busy, too expensive and, in fact, often less experienced in dealing with small residential projects on ‘normal’ budgets.

So I wanted to create this platform for those design professionals I know who are suitable, experienced and eager to take on domestic projects like yours. They are often small, young practices or freelancers. The problem was that, before Design for Me, they were very difficult to find! All you need to do is tell us a bit about your project…


Emily  Design for Me

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138 Responses to “How Much Does a House Extension Cost?”

  1. john hughes

    We are contemplating an extension 5m x 3m. this will be either single or double depending on price. Can I have a price per m for the midlands please

  2. Dave

    Looking to do a side extension around 5m wide 7m depth with a pitched roof. Planning permission is in we are based in Hampshire. Any ideas of cost to put up a basic single story extension with basic fittings i.e. electrics, plumbing and plaster finish?

  3. Sam

    We are looking for a single storey reat extension 4m x 10 m in South tyneside. Pitched roof, with a knock through into the original house. Pitched roof and bi folding doors.
    We also need a loft conversion with rear dormer.
    Have plumber and electrician so just the building costs. Any idea of costs?

  4. Mel

    We are in the North East and looking for a reliable builder – anyone got recommendations ? Thanks !

  5. Norna

    We’ve had plans drawn, single extension and knock through. Adding a porich extension so we can have a larger hall, moving our toilet forward. And have been told it’ll be about 80,000? Is this about average?

  6. wendy

    Hi we are based in Essex and are looking at have a single storey extension – which should double the size of our kitchen. We have a surface water pipe which runs alongside our house so we can’t build on it just alongside it. I have heard you can build single storey extensions without excavating the ground using a steel base. Has anyone done this and should we use a specialist company?

  7. ricoh

    Hi Gerry, thanks for the post, would you please be able to tell me how the structural engineers designed the steel frame for your extension? I’m looking to use as little steel as necessary for my extension. thanks. Ricoh

  8. James

    Hi, Cranbrook, Kent area of South East. Looking for rough cost of small 2-storey extension to rear of our semi-detached 1950’s house. Only a 10m2 footprint on ground floor, 1st floor identical size. (2.5m x 4m) Not fussed about roof shape, happy with cheapest. Simple decoration inside, nothing fancy. Simple windows put in up and downstairs, radiator added to each room, + extended pipework. Is a budget of £30k too little to hope for, for such a small extension?
    Thanks for any info!

  9. Johnathan Norton

    Hi very useful read, thank you. We are considering a side return extension on our ground floor flat in SW11 Battersea. roughly 4m x2m x3m, do you have any idea of cost and a recommended arcitect / capabe project manager?

  10. Sheff Sul

    Hi Pete

    Im the director at portlands building and maintenance was wonderjng if you had your works completed were bassd through out london and will be happy to give you advice to carry out any works!


    Sheff Sul

  11. Sheff Sul

    Hi All

    My names Shef Sul I have my building company based in london and I’ve notice allot of you guys are having issues with regards to getting the right builders at an competitive price my company has many experience in lofts and house extensions through out london be free to email me to discuss quotes or even to have a conversation regards to your current projects!


    Portlands Building and maintenance!

  12. D AND J Advanced builders

    this site is very helpful for clients.we are general builders in Birmingham and East London for the past 25 years with great reputation.
    we work with a number of high profile clients. working with extensions, restoration refurbs, ground work and flat conversion is our typical work. we have fully qualified tradesmen.

  13. Steve

    Hi Pete
    I just came across your post although i appreciate it is some time ago and wondered if you managed to get fixed up with a building contractor on your project yet?
    We were simply gauging the market in and around London as we have just been commissioned on a project in Watford and it seemed worth exploring other opportunities in this part of the UK.
    Our main function is providing architectural services from design to project management but we also offer residential construction services.
    Please let me know if you are interested in discussing your project.
    Many thanks

  14. Bhavik

    I’m in planning process currently and looking for a rough price.
    I’m looking for a double story side extension which will 3.8m in length and 8/9 meters high.
    With this i will do a rear extension which is 9.2m wide and 4.5m in length.
    What would be a rough cost for this?

  15. Jolanta

    Hi, where about are you based? Can you share the builders contact details please? Thank you.

  16. Sharon

    I am looking for a builder, want an extension on the back average size and has planning permission. I want new kitchen as our one is very small so the extension would be built on the patio.We are mid terrace and neighbours are fine with this. Would like a quote. We live in London E17 and have been given some ridiculously high prices.

  17. Carol

    I thinking of building another bathroom over the existing one. How much will it cost? Do i need it to tear down the existing one & rebuild with a 2 storey? Will party wall come into the picture as the existing one is attached to the neighbour’s extension?

  18. Sheila Jones

    I am thinking of buying house to renovate..semi, i am thinking double side extension and rear extension , probably knocking down of a wall, patio front and back, render house , fit kitchen and new bathrooms , in essex”’ can someone give me a guide price for the whole works Please including plans , skips mixers etc. Ta

  19. Lara

    Hi Ola, have you finish with your refurb? I’m looking for contractor, any recommandation? I’m planning to have a double storage extension. Thanks

  20. Ross

    Hi Jill

    I seen your comment regarding possible building works. We are based in Fife and would welcone the opportunity to discuss any potential works you require.

    Kindly drop me an email should you still be looking to progress.

    Kind regards

    Ross Hunter

  21. Michel

    i have plans and i am currently looking for a builder in the st albans area to do a quote for me.

  22. Tony

    We used MIRABILE construction &renovation company based near Bath. The price worked out to be around £1350 per square metre. Really impressed and will use them again. I found them on face book from a recommendation.

  23. Charlotte

    Hi, I have found your facebook page and saved it as we are going to be looking for a builder to build a 2 storey extension to the side of our house, 11×3.5m. We are based in South Manchester. Just getting an architect to draw up the plans and then we need to see if it is within our budget.

  24. Ahmed

    Have you found an architect and construction company to build your extension. if not our number is 0207 1012569

  25. Dee

    Wanting some quotes for double storey extension approx 12 ft by 24 ft downstairs kitchen dinner window at front double doors to back. Upstairs one large bedroom with en suite window at front and side window in ensuite. Any idea on cost as riugh guide appreciated. Bathroom will be next to one already there kitchen will extend across from one I have i.e. remove wall

  26. Gav innes

    You are being robbed am building the same size in glasgow for 18 grand search about mate

  27. Nav

    Hi, I’m looking for a very rough idea of cost to build just the foundations/ slab for a 4x9m single story extension. There’s a manhole adjacent to one side of the foundations, and an inspection hole roughly in the middle, two mature trees around 6m away so foundations will likely need to be a little deeper than usual for building regs…

    Just a ball park figure please if anyone can assist? The build is in Worthing, West Sussex if it help. Thanks.

  28. Mo

    Great post and really informative. We are at the very early planning stage but are looking to extend sideways. 5m x 4m for a wet room and living space for my disabled relative. We are in the North though. Do you have services up here.

  29. Nisha

    Hi there, I’m looking for builders to quote for a kitchen side return extension in the SW11 area. Can you please let me know the name of your Company and which post code you cover. Kind regards.

  30. Robert

    Hi Sarah. Iam based in Milton Keynes and could help if you still need your job doing ? Regards Robert 07899904882

  31. Suzanne

    Hi Darren I was wondering what the cost per sq r are in bucks for an extension probably 2 storey as we are trying to work out how much an extension would be before buying a house to renovate in bucks? Thanks

  32. Patricia

    Thank you for this. It helps to sift through chancers and builders who don’t think they have the God given right to share in what the others think your property value will increase by! Excellent piece.

  33. RAY

    Hi Tony

    Ive been looking for a good builder for a while now , I’m wondering where about is he based ?

  34. Dave Cox

    Hi, I am moving within the month and am looking for costs to extend above a double garage, just really rough guide, Southampton area.

  35. louise

    Hi , We have plans for an extension above our double garage. It is a half storey extension approx 5m by 6m . WE hope to get a master bedroom with ensuite. For the Shell alone, ( no fit out for bathroom , we have been quoted from 27k to 53K , this is a very straight forward build, removing the existing garage roof and raising it and recycling roof tiles again. Any help would be appreciated, we are in scotland.

  36. Jan

    Who was the builder and where is he based please, I am ringing around for quotes and getting nowhere

  37. Sarah

    Hi. If we were looking to do a rear extension on a chalet style house, and were looking to knock the current kitchen and dining room into one and add on a 3m x 7.5m two storey extension, what kind of build costs would we be looking at please? the only thing being put in would be a kitchen (not worried about the cost of that at the moment) but if the extension is brick on the ground floor and then block with cladding on the first floor, can anyone give me a rough estimate? don’t want to go ahead with a possible purchase if we cant then afford to do the extension. thank you!

  38. Ranjit Savant

    Hi , I am looking for a potential extension and with kitchen and bathroom.also the plumbing / heating of the entire house and electricals.

  39. Pete

    Hi, I have had quotes for a wrap around side and rear extension which vary substantiallly from £150 to £270k. The extension is 3m to the side and rear circa 65sqm of a mainsonette flat (ground floor) with good access in SW London. It will involve a new bathroom and kitchen with 3 x 1*1.5m roof lights and 6m sliding doors. We can only afford around £100k so i am thinking I may need to build the shell and PM/finish some of the work myself as much as possible to save. Any recommendations or builders willing to work with this would be welcome. Thanks

  40. Gerry

    Hi. I’ve recently had an extension built 6m width x 4.5 m length out from the existing back wall of the house. Total cost for the build including vat but excluding architects drawings Building Regs/ Steel calculation fees was £38k. Needed to add on another £1500( – for Drawings £750, Building regs – £500 and steel Calcs £250) so looking at 40k odd. Add on new large kitchen, fitting and putting down Karndean flooring and no change out of £50k.

  41. Billy G

    What would the build cost pm2 be if I was to do the groundwork (dig and footings)? We’re in the South East.

  42. marie

    Hi Ola Oni,

    I wonder if you have managed to find your trusted building company. If not I would advice to get in touch with ( they have done two project for me in London and I could not be happier.


  43. Jan

    Hi I’m looking to build a single storey extension on a bungalow in the midlands area 35ft wide x 10ft out shower room to be added any idea how much this should cost and does anyone know any good builders out there

  44. Rob

    Looking for experienced and reliable builder to quote for a single storey extension in SE London. Approx 15 square metres on relatively straight forward new build.

  45. Grafters

    We are a building company in West Sussex covering all aspects of building and property services . extensions from £1100 m2

  46. Sam

    Hello, we are looking to extend next year and are keen to get some prices and work booked in. We are based in Caterham, could you quote?

  47. Martin davis

    Hi am looking for quotations for loft extension (dormer I think)and single storey rear extension . Am based in London borough Redbridge . Thx

  48. Phil

    Hi we are debating between a small single storey extension 3mx3m or a conservatory. With a budget of about £12k any recommendations?

  49. Mike Watkins

    Great article! we are a design and build company based in Solihull, West Midlands. We carry out extensions, loft conversions, renovations and new builds across the west midlands and warwickshire.

    we can be contacted on 0121 369 1048 or email

  50. Graham

    Hi there, some very good advice on this site.

    Just brainstorming at present, we moved to a newbuild last year and love the area but bedrooms may end up being a bit small for our boys. We are in a Persimmon Newmore style, floor plans can be googled. There is space out the back to extend, a possibility (depending on cost) might be to have a 2-storey from the dining part of the kitchen, hopefully retaining the French doors which would be placed on the new side wall, and extending the smaller Bedroom 3 above, hopefully retaining the window, this would be a footprint of about 2500×2500. Hope that makes sense. Is that a feasible project and would the amount of extra room be worthwhile for the cost and disruption?

    The other thought I had was to convert the loft with ladder stairs up from bedroom 3, I had believed it might be easier/cheaper than external extension but having read up elsewhere on what was involved, maybe not worth the hassle.

    Any comment would be much appreciated. 🙂

  51. lenka

    Hi there! I am thinking about buying and I am looking for properties where value could be added in a future.
    Does anyone here have over carport extension? I can’t find proper price range anywhere.
    It would be about 25m2, 2 bedrooms and 1 tiny shower room. Based in NW.
    Thank you all in advance!!!
    It is really going to help me to meke decision about one house.

  52. Dave Chera T/A DC Design & Develop

    we are from East Midlands but we work anywhere depends upon size of project.
    Phone number-07710194967

  53. Dave Chera T/A DC Design & Develop

    We do every thing in building right from landscaping to build new houses. Depends upon size of project we are flexible to work anywhere in the country.

  54. matteo

    Hi Robert, how much for a 20 sq meter siBirmingham, Shirley, Solihull near motorway J4 M42?

  55. Matteo

    I am unsure if it is better add a granny flat or split the house into 2 flats, as we are going to Australia, whatever gives us the highest return of investment, it will be our best option… Do you have your own experience architect?

  56. Jack Mizon

    Fantastic thread guys, we’ve been in the industry 25 years and all your numbers pretty much add up. As has been said builders will go in low to get you in then throw in all kinds of add ons! Get a signed agreement on costs which is what we do with all our customers. All the best with your projects!

  57. Anne Scogg

    I live in Northamptonsire and am interested in having a 1.65×8.5mextension across the rear,of the house to extend the existing lounge and dining room. I would like a pitched roof with velux roof windows and bi folding doors. Ttki

  58. Carl chamberlain

    Hi Neil we are a construction company based in the north west we do all aspects of building from new builds ,conversions and extensions we have a fully equipped joiners shop where we make all manor of things from garden office pods to kennelling systems and everything in between .we would gladly give you a quote if you still need one please check our website or Facebook page
    Bryn Hall Construction
    With thanks Carl

  59. Neil

    Planning a garage conversion and going up 1 story to extend a bedroom and put in an ensuite. Live in N Wales, near Chester. Grateful for a steer as to any reliable and reasonably priced builders. Helpful to know ballpark costs – good article.

  60. Robert

    I run a building company in Southampton, Shield Building Services (Uk) Ltd
    You can find us in
    I would estimate your extension to cost £18,500.00

  61. Lisa

    I am looking to extend my 3 bed 1939’s semi house with a 5m X 4m extension. More than likely it will have to be a single storey extension due to the probable cost but would still like to explore the option of extending upstairs too.
    I am in Colchester, Essex. Can anyone recommend a builder or give me an idea of cost?

  62. JOHN Pitt

    Hi Jill. where are you in Fife? I am just outside Stirling and if not to far could poss look at the work you are planning and advise.

  63. steve wright

    hi im getting asked all the time …how much for the dig ,slab the bulld nothing else all the time …labour only eg single storey ext 3.5×5.4 brick and block …whats the cost ????most ask question m/c area

  64. Sebastian

    This article give basic ideas to client how much can be cost extension but not always is working like that.
    I working in London area, we try not estimating work per sqm with materials because different extension need different work. Price is depending of foundation what you have designed, how many lintels you need to put, about changing in plumbing and waste pipes, roof construction and cover and about materials quality as well. Some places need more solid or additional damp-proofing to prevent problems in the future.
    I think client should have right to choice materials quality what will be used in his place.

  65. Ola Oni

    Hi Harry and other reputable builders kindly contact me for a rear ground floor extension by 3 meters and a single dormer loft conversion both within permitted development plus a full house refurbishment. Its 1100sqft currently and will be 1497sqft at completion. We have been quoted on average £98k+VAT and £120k+VAT and £130k+VAT. I am thinking it should be in the region of £80k+VAT.

  66. bryan

    I presume the prices are all inclusive i.e. labor etc. It depends on how competent you are, how much time you have. If you can get a builder to work more as an advisor, inspector, then doing the unskilled, or semi skilled work will dramatically reduce the cost. I have the good fortune of a retired builder as a father, he no longer get his hands dirty, but will tell what needs doing, regs etc. I do the hard work, foundations, roofing, plastering etc, then before the local authority inspect he comes round and tells me if all good. So it can be done for a lot less, the challenge is finding a builder who would be interested in doing part or some of the really tough/complex jobs and let you do the rest. Most are an all or nothing option. I learnt to plaster, the cost for my whole house was a couple of hundred pounds, its still on the wall 3yrs on. Kitchen was £4k including all appliances. It can be tough and sometime soul destroying, and when I have had money there is nothing better than going away and a builder doing the work for you. But if your on a budget it can be done. Plus a certain satisfaction that you did it yourself.

  67. Paul

    Hi, we are a building company in South Yorkshire and agree this is a great starting point for any addition to your property. Great article .

  68. Dmitri

    Hi James,
    From our experience, for kitchen/diner this will be a good size extension. Add 3 medium sized Velux windows to pitched roof and it will be very light and spacious. It can be done for £50-52k

  69. Ray Nash

    The extension we have in mind is single storey, 4300mmX4000mm with open access thru ano room, this will need an extended lintel, but will retain the existing depth from the conservatory doors its replacing so no upstairs work required. We want a flat roof with a 2m x 1m non opening raised flat roof light central, 2 sets of aluminium bifold doors (out folding) 2.5m approx each, meeting at the corner but with a small return brick or steel pillar for support at the corner, To include basic electric wiring with LED downlight around roof light and electric underfloor heating. Walls and ceiling to be plastered internally. What price should we be expecting? We already have outline plans from an architect. Southampton area.

  70. Lyndsey

    Hi, I found this site very useful when we were planning our build. We live in SW London but used the £1200 as a starting point knowing that central London is going to be more.
    We have quite a straight forward rear extension and looked to put the money into the finishes and did a lot of legwork sourcing these ourselves.
    We obtained several builders quotes which were different by £40k?!? You do wonder if you are missing something when there is such a difference in quotes, but we went with a builder who was recommended and could not be more happy with everything.
    I guess the basic build was around £1500m2.
    We are hoping to get our loft done later this year and will be using the same team.

  71. Rachel

    Hi, what area are you based in? Sounds like a good deal

  72. Omer/Mixwall Ltd

    Hi James, your prospective extension area is perfect for kitchen diner, but as it is almost square shape, you better off designing the kitchen as L shape so u can divide the space as 2 rectangular areas that can accommodate a large dining table, to work the existing kitchen pitched roof into the design, depends on the angle of the pitched roof,
    finally, we could confirm a budget of £1200 per m2 for your size,

  73. Matthew Koumis

    Hi! I am looking for a quotation for a 40 sq metre kitchen extension in Winchester with hard wood floor and sliding door. Are you able to give me a ball-park estimate? Many thanks.

  74. Nina

    Hi did you find a builder . What price was you quoted . We also huntingdon could you recommend a builder.

  75. James

    Hi. We are looking at buying a house on the SW London/Surrey border that has a small pitched roof kitchen on the back. We want to understand the likely cost of building a kitchen diner across the entire back of the house likely dimensions 6.2 x 5.7m. Firstly is this a decent size for a kitchen diner – secondly would the £1500 per m2 number be about right? Could the existing kitchen pitched roof be worked into the design?

  76. Carla

    Hello..What area is your builder in? Can you provide a contact name and number? Thanks.

  77. Design for Me

    Hi Matt,
    We’d be happy to help you find some architects to speak to about this. Once you’ve posted your details to the site (what you’ve written here would be fine) we’ll send it out to our database to see who can help you… It’s all completely free! If you want to appoint one of the architects for your job, You’ll agree a fee with them after your first consultation. Here’s a link to get started: Post your job

  78. MATT

    Hi finding this site really useful, I’m looking at building a side extension on my house. roughly 5m by 4m, the ground floor is mainly a single garage with 2 small rooms running down the side nearest the house ( utility and downstairs WC ) upstairs I just want a single bedroom possibly with a ensuite. will the price for downstairs be cheeper as the majority is a garage, block walls interior no plaster etc ? also if I just want the basic shell without finishing for the upstairs would this keep the costs down as I would like the new bedroom space but may need to finish this room at a later date ?

  79. Jill

    We are considering 2 options for extending our 100 year old terraced cottage. Renovating and extending the 2 storey barn-type building on the side of the house or doing a 2 storey extension to the rear. We are in Fife – any suggestions on who to speak to to help us understand the costs and benefits of each option, and to plan a reasonable timeline?

  80. Mokah

    Well thought out website and very informative.
    I am looking for reliable builder for double storey rear extension 6 x 3 meters as well as garage extension in Huntingdon, Cambridgeshire.

  81. Krish

    I am looking to configure my kitchen dinner with potential extension so could you please share the details of your Architect and builder .
    Thanks in advance and good luck with your building .

  82. Caroline Foy

    We are in West Yorkshire.
    Currently in a 3 bed semi detached and wanting advice on creating more space in our home. Possible options building an integrated garage which we can then convert, a single extension or double extension on the side of house. We need support to explore the options and costs ?
    Thank you

  83. Krish

    Hi, Our kitchen is small so looking to knock the wall I between the dinner and reorganise the kitchen for space . Also looking to extend to get bit more space but not sure. So looking to get an architect to access the potential For space and access staged development. So any reference would be helpful .

  84. Mark

    I am based in Manchester, and really want to Add two bedrooms to the house, but i dont know what would be be easier/better, get the loft converted and loose the box room to stairs, or get a two story extension and add a lounge/utilityroom/downstairs loo.. Which would be more cost effective assuming a budget with no wiggle room to go more than £80,000

  85. Harry

    We are a building firm that has been working in the industry in the South East for the past 15 years with a great reputation. We work with a number of high profile clients and firms. We are increasing the size of our team so that we remain more efficient with work load. Working with extensions, loft conversions and flat conversions is our typical work. We have fully qualified electricians and gas engineers on board. Beware of cowboy builders and builders that do not have good reputations; that may under quote to get the initial job on and that ask for more money. Our quotations are clear, finite and offer no obligational advise. Our prices are very competitive.

  86. Sinead Simpson

    We are adding on a single storey 20m2 extension, just had first quote back at 41.5K, this seems very high to us as our architect said we should be looking at around 20-25K.

  87. Darren Smith

    Hi Sarah
    If you are still struggling to find a builder to provide you with a quotation we would be more than happy to.
    Many thanks

  88. Adrian

    Hi Michael,

    Looking for a genuine quote. We have had a builder change quote substantially from £30k to £50k (+ vat) for a single story 2m x 6.3m extension. Includes a 2.4m bifold and 6.5m and 3.5m steels in a T. Only 6 weeks until job commences and we have been hit with this increase. We are about to go out to tender. Would you be interested (OX14 – Abingdon).

  89. Melvin Griffiths

    Looking for a quote for either loft or kitchen extension

  90. Lucy

    hi, I’ve been after an answer like this for ages so thanks for such a great article!!
    I’ve been looking at having a 6x4m single storey extension but my husband will be taking on a lot of the work and having only labourers in for the work that he won’t be able to do (plumbing, electrians, plasterers etc..) how much would u think the cost would vary?? We are thinking of a budget of £25,000 which will also have include a kitchen and a downstairs loo. Many thanks

  91. Lynette

    Hi,we are looking to get rough price guide on 2 storey extention on back of house,extend kitchen,move bathroom back upstairs,extra space in 2 back bedrooms?. Thank you?

  92. Sarah

    Hi, I noted your comment on this website – where are you based? I am looking for a builder to provide a quote for a 4 x 4 single story extension (have planning approved and building regs approved) and I live in the South East (Bucks). I am really struggling to get responses from builders to quote for work!

  93. Julie

    We are looking to extend to the side but so the house is L shaped with a single storey garden room approx 5×5. What cost implications can you foresee? We are complete novices but really need to keep costs down.

  94. Tony

    I am half way having an extension built , it’s external measurements are 4m x 4m . The quote was £19,000 which included demolishing and removing an old conservatory . Also building a solid retaining wall along 3 sides. The quote did not include decoration . The builder is not VAT registered so there is no VAT to add. I hired an architect to draw the engineering plans for £250. The builder came highly recommended and has been excellent. I reckon I got a fair deal

  95. James

    I live in an end terrace house (block of about 6 x houses). Because I am one of the “ends” of the block, there is a “right of way” permitted by the neighbours (which is fine), so that in the event of fire services (or whatever) needing access, they could. My question is simply “If I put an extension on the back of my house, can I ‘move’ that right of way location”? I’m presuming that as long as the right of way (gate in my case) still exists, that would be fine?

  96. lisa

    I getting prices for a 5.2m x 3m extension with a Mono pitched roof with 3 Velux windows, french doors and 1 window. Along with this I am getting 2 beams at 5 metres installed to open up into the new extension. the ceiling internally is vaulted to match the roof pitch. There is other minor works. Is the £1200 per square metre a good guide to use for this type of work or should I be looking at a greater cost per square metre.


  97. richard

    What are the size limits on extentions before you need planning permission, and if you can build say a 10 foot out and 20 foot long single story extention on the rear of your house without planning permission, could you then add a 10×10 conservatory onto that without planning also? or does it depend on the size of your garden and house?

  98. Design for Me

    Hi Uzma, Sounds like an interesting project. Your budget will need to be looked at in conjunction with speaking to architects/designers in the first instance. Your design professional with work with your brief and budget to come up with solutions. They can help you figure out where to spend the budget and more importantly where to save. If you’d like to set up some meetings with some architects/designers you can post your job for free here and we’ll help you find the most suitable for your needs:

  99. Christian

    Hi Great Article, thank you. Do the costing’s include VAT or will 20% need to be added?

  100. Uzma Mirza

    I would like to have a single storey reae extension, knocking down the existing kitchen which was extended without permission by previous owners. Also to move the bathroon=m from existing position to icrease space and create a second reception and then extend out the kitchen and bathroom.
    My budget would be at the highest £20,000.

  101. Adrian

    So so informative given everything else there is to think about when trying to plan a project, well done for being so informative. All I need to know now is how much to expect to pay for architect fee’s?

  102. mark

    £2250 as a estimate that’s fine but needs working out properly and vat has to be added 1/2/2016

  103. Jamie

    Was your extension within the perimeters of the £1200 per metre square mark? Also how big? Sorry to quiz but I’m trying to gauge the usefulness of the £1200

  104. Michael Tokarski

    Well done all at youdesignforme, I’m a hands on builder and have been working in my industry in excess of forty years ( primarily bricklayer Carpenter but do all the the ground works while using qualified technical subcontractors and other sub contractors when needed for program adjustments). This well thought out website should be a good guide to the house owners who are expanding or improving their house for either economic or investment purposes, iv’e found that it’s difficult for people to fully understand the variable cost through either design change or a project taking longer to start and then incurring extra labour or material cost. On my last project the variables were on heating and electricals because not enough research was done on these two points initially.
    This site is a very good starting point.
    I have compared your guide of cost to my estimates over the period of the last twelve months and we are quite close.

  105. Stewart Hilton

    I’m wondering whether the same applies to an above garage extension. Garage adjoins neighbouring garage and the house is less than 20 years old. The garage is converted already. The dimensions are standard, I believe, 18 feet by 8 feet 6 inch.

  106. Gavin

    In Eastbourne, I’ve recently been quoted around £32k for a single storey 4 x 3m kitchen extension. No frills, and not a difficult job – no obstacles to the build – but the SE costing seems to apply.

  107. dave

    That a very good method, I’m a builder and it tends to work out about £800-£1000 a square meter.

    A lot of company out there going in lower but add more costs on at a later date.

    So beware of them

  108. Jonathan

    Very clear written. A simple way to cost an extension. including additional elements.
    If the £1,200 per square metre holds it will be very usefull as a guide.

  109. Jamillatu kamara

    Looking for architect for extension of kitchen dinning , bathroom and a room

  110. Ross John Daniel

    I am currently compiling the osts for a two storey extension project and this little article has been a fabulous tool to gauge my expenditure! Thank you!

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